JP5929521B2 - Motor control device and electric power steering device using the same - Google Patents

Description

  The present invention calculates each phase duty command value for controlling the motor current by control calculation, forms a PWM (pulse width modulation) signal corresponding to each phase duty command value, and outputs the PWM signal from the inverter to the motor. The present invention relates to a motor control device that is driven by applying a command current (voltage), and also relates to an electric power steering device that uses the motor control device to apply assist force by a motor to a steering system of a vehicle. In particular, a single current detection circuit (one shunt type current detection circuit) is arranged on the power input side or power output side (ground side) of the inverter for PWM control, and each phase PWM signal is made to correspond to the carrier cycle. Shifting and fixing, generating a current detection timing at which the PWM signal is turned ON simultaneously at one phase or two phases at a fixed position of the carrier cycle, and detecting and processing the motor current at the current detection timing, thereby reducing the size. The present invention relates to a motor control device that is reduced in weight and costs and an electric power steering device that uses the motor control device.

  An electric power steering device that applies a steering assist force (assist force) to a steering mechanism of a vehicle by a rotational force of a motor, a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer. A steering assist force is applied to the vehicle. Such a conventional electric power steering device (EPS) performs feedback control of the motor current in order to accurately generate the torque of the steering assist force. In feedback control, the motor applied voltage is adjusted so that the difference between the steering assist command value (current command value) and the motor current detection value is small. In general, the adjustment of the motor applied voltage is performed by duty control of PWM control. It is done by adjusting.

  A general configuration of the electric power steering apparatus will be described with reference to FIG. Then, it is further connected to the steering wheels 8L, 8R via the hub units 7a, 7b. Further, the column shaft 2 is provided with a torque sensor 10 for detecting the steering torque of the steering handle 1, and a motor 20 for assisting the steering force of the steering handle 1 is applied to the column shaft 2 via the reduction gear 3. It is connected. The control unit (ECU) 100 that controls the electric power steering apparatus is supplied with electric power from the battery 13 and also receives an ignition key signal via the ignition key 11. The control unit 100 calculates a current command value of an assist (steering assistance) command based on the steering torque Tr detected by the torque sensor 10 and the vehicle speed Vel detected by the vehicle speed sensor 12, and compensates the current command value. The current supplied to the motor 20 is controlled by the voltage control value E subjected to. The vehicle speed Vel can also be received from a CAN (Controller Area Network) or the like.

  The control unit 100 is mainly composed of a CPU (or MPU or MCU). FIG. 2 shows general functions executed by programs in the CPU.

  The function and operation of the control unit 100 will be described with reference to FIG. 2. The steering torque Tr detected by the torque sensor 10 and the vehicle speed Vel from the vehicle speed sensor 12 are input to the steering assist command value calculation unit 101, and an assist map is displayed. The steering assist command value Iref is calculated using this. The calculated steering assist command value Iref is limited in output by the maximum output limiter 102 based on overheat protection conditions and the like, and the current command value I whose maximum output is limited is input to the subtractor 103.

The subtraction unit 103 obtains a deviation Iref4 (= I−Im) between the current command value I and the motor current Im of the motor 20 that is fed back, and the deviation Iref4 is controlled by a current control unit 104 such as PI (proportional / integral). The controlled voltage control value E is input to the PWM control unit 105 to calculate the duty command value, and the motor 20 is driven via the inverter 106 by the PWM signal PS calculated from the duty command value. The motor current Im of the motor 20 is detected by the current detection circuit 120 in the inverter 106, and the motor current Im is input to the subtraction unit 103 and fed back. When the motor 20 is vector-controlled by the dq axes, a resolver 21 is connected as a rotation sensor, and an angular velocity calculation unit 22 that calculates an angular velocity ω from the rotation angle θ is provided.

The inverter 106 that controls the motor current Im with the voltage control value E and drives the motor 20 uses a bridge circuit in which a semiconductor switching element (FET) and the motor 20 are bridge-connected, and is determined based on the voltage control value E. The semiconductor switching element is ON / OFF controlled by the duty command value of the PWM signal thus controlled to control the motor current Im.

  When the motor 20 is a three-phase (U, V, W) brushless DC motor, details of the PWM control unit 105 and the inverter 106 are configured as shown in FIG. 3, for example. That is, the PWM control unit 105 inputs each phase carrier signal and calculates a voltage control value E for PWM-Duty command values D1 to D6 for three phases (U, V, W) according to a predetermined formula. 105A and a gate drive unit 105B that drives each gate of FET1 to FET6 with PWM-Duty command values D1 to D6 to turn on / off, and an inverter 106 includes an upper stage FET1 and a lower stage FET4 of the U phase. The upper and lower arms are composed of a three-phase bridge composed of an upper and lower arm composed of an upper FET 2 and a lower FET 5 of V phase, and an upper and lower arm composed of an upper FET 3 and a lower FET 6 of W phase, and PWM-Duty command values D1 to D1 The motor 20 is driven by being turned ON / OFF at D6. In addition, power is supplied to the inverter 106 from the battery 13 via the power relay 14.

  In such a configuration, it is necessary to measure the drive current of the inverter 106 or the motor current of the motor 20, but as one of the required items for the compactness, weight reduction, and cost reduction of the control unit 100, the current detection circuit 120 There is unification. A single shunt type current detection circuit is known as the unification of current detection circuits, and the configuration of the single shunt type current detection circuit 120 is as shown in FIG. 4 (for example, Japanese Patent Application Laid-Open No. 2009-131064). ). That is, one shunt resistor R1 is connected between the bottom arm of the FET bridge and the ground (GND), and a voltage drop caused by the shunt resistor R1 when a current flows through the FET bridge is an operational amplifier (differential amplifier circuit). ) 121 and resistors R2 to R4 are converted into a current value Ima, and further A / D converted at a predetermined timing by an A / D converter 122 through a filter composed of a resistor R6 and a capacitor C1, and a digital current value Im is obtained. It is designed to output. In addition, 2.5V which becomes a reference voltage is connected to the positive terminal input of the operational amplifier 121 through the resistor R5.

  5 shows a connection diagram of the battery 13, the inverter 106, the current detection circuit 120, and the motor 20, and the U-phase upper FET 1 is ON (lower FET 4 is OFF), and the V-phase upper FET 2 is OFF (lower FET 5 is ON). , A current path (broken line) in a state where the upper stage FET 3 of the W phase is OFF (the lower stage FET 6 is ON). Further, FIG. 6 shows a state where the upper FET 1 of the U phase is ON (lower FET 4 is OFF), the upper FET 2 of the V phase is ON (lower FET 5 is OFF), and the upper FET 3 of the W phase is OFF (lower FET 6 is ON). Current paths (broken lines) are shown. As can be seen from the current paths in FIGS. 5 and 6, the total value of the phases in which the upper stage FETs are ON appears in the current detection circuit 120 as a detection current. That is, the U-phase current can be detected in FIG. 5, and the U-phase and V-phase currents can be detected in FIG. The same applies to the case where the current detection circuit 120 is connected between the upper arm of the inverter 106 and the power source (battery 13). 5 and 6, the connection of the resolver 21 and the power relay 14 are omitted.

As described above, when the current is detected by the current detection circuit 120 in the one-phase ON state and in the two-phase ON state and the characteristic that the three-phase current sum is 0 is used, each phase current of the three phases Can be detected. In the case of FIG. 5, the U-phase current I _U is detected, and in the case of FIG. 6, the total value of the U-phase current I _U and the V-phase current _IV is detected by the current detector 120. However, in the case of three phases, there is a relationship of I _U + I _V + I _W = 0, so that the W phase current I _W is detected as I _W = − (I _U + I _V ).

  However, in the inverter 106 composed of a single current detection circuit 120 as shown in FIG. 4, the influence of noise components such as rigging noise generated by the current flowing through the current detection circuit 120 immediately after each FET is turned on. It is necessary to remove and detect an accurate current. In addition, when the interval between the timings when the FET is turned ON / OFF between one phase and the other phase becomes very short, the current required for current detection does not flow through the FET, or the dead time (dead zone) ) And the delay in the response of the circuit, the current cannot be measured accurately. When the A / D conversion unit is used in the current detection circuit, in order for the A / D conversion operation to be performed normally, signals of the same magnitude must be continuously input for a certain period (for example, 2 μs or more). This is because the A / D converter cannot detect an accurate current value unless a stable signal is continuously input.

  Therefore, it is necessary to continue the one-phase ON state and the two-phase ON state for a time required for current detection. However, when each phase Duty command value is approximate, there is a problem that the time cannot be secured.

  As a solution to such a problem, a motor driving device disclosed in Japanese Patent Application Publication No. 2005-53270 (Patent Document 1) and an electric motor driving device disclosed in Japanese Patent Application Laid-Open No. 2003-189670 (Patent Document 2) have been proposed. ing. In the device of Patent Document 1, a PWM pattern (PWM signal) that is in a 1-phase ON state and a 2-phase ON state only for the time required for current detection is determined by a magnitude relationship between each phase duty command value and a space vector method. A PWM pattern is output. Further, in the device of Patent Document 2, the duty command value is corrected so that the time required for the one-phase ON state and the two-phase ON state can be secured for the time required for current detection, and the increase / decrease by the correction is adjusted in the next carrier cycle. The average value is the same as the original duty command value.

JP-T-2005-53270 JP 2003-189670 A JP 2010-279141 A

  However, in the apparatus disclosed in Patent Document 1, in order to actually output a PWM pattern by the space vector method, it is necessary to use a CPU corresponding to a space vector that can set ON / OFF of a PWM signal at an arbitrary position in the PWM cycle. There is a problem that a general PWM timer using a carrier signal cannot be used, and the current detection timing needs to be variable, so that current detection is not easy. Further, in the apparatus disclosed in Patent Document 2, the duty command value is changed, and the changed amount is corrected in the next carrier cycle. Therefore, the motor current vibrates due to the duty change within 2 PWM cycles. As a result, there is a high possibility that the torque ripple performance and the operating sound performance will be deteriorated, the current detection timing must be variable, and the current detection is not easy.

  Furthermore, in the electric motor control device disclosed in Japanese Patent Application Laid-Open No. 2010-279141 (Patent Document 3), a method of determining the maximum duty, intermediate duty, and minimum duty and sequentially rearranging the shifted carrier period. Is used. Therefore, in practice, there are surprisingly many arithmetic processes in the process from the determination of the maximum duty, the intermediate duty and the minimum duty, and the allocation to the shifted carrier period. Specifically, when the duty after the determination of the maximum duty, intermediate duty, and minimum duty is directly reflected in the shifted carrier period, output timing and sudden change of the duty for each phase (extreme rearrangement) occurs. Therefore, a current hunting phenomenon occurs, and smooth motor current control cannot be performed. For this reason, in the apparatus described in Patent Document 3, it is necessary to eliminate the sudden change in the Duty setting until the Duty after the determination of the maximum Duty, the intermediate Duty, and the minimum Duty is reflected in the shifted carrier period. Since the duty is gradually changed to Duty, there is a problem that high-speed and precise calculation is repeatedly performed, and a large amount of processing power of the CPU is consumed.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to solve the conventional problems of a motor control device using a single shunt type current detection circuit and an electric power steering device using the same. That is, by generating the current detection timing at which the PWM signal is turned ON simultaneously at one phase or two phases at a fixed position of the PWM cycle, it is not necessary to perform software control frequently (for example, every 50 μs). A motor control device that maximizes the duty range that enables current detection after reducing the processing capacity of the CPU while reducing the size, weight and cost, and an electric power steering device using the motor control device It is to provide.

The present invention calculates each phase duty command value for controlling the motor current by control calculation, forms a PWM signal according to each phase duty command value, and controls the motor by an inverter based on the PWM signal. With respect to the motor control device to be driven, the object of the present invention is to connect a one-shunt type current detection circuit having an A / D converter to the power supply side or the ground side of the inverter, and to each duty command value . The corresponding PWM signal is fixed at a predetermined position of the carrier cycle, and has a function of shifting the PWM signal in a predetermined direction. The current detection timing for detecting each phase current of the motor and performing A / D conversion is set at the predetermined timing. It is achieved by fixing the three points so as to correspond to the position, the current detection timing, and the predetermined time offset position rearward from the forefront of the carrier cycle, the key More effective by fixing to the center of the rear period and a position offset by a predetermined time forward from the end of the carrier period, or the predetermined time being 0 to 4 times the dead time of the inverter To be achieved.

Further, the present invention calculates a duty command value for each phase for controlling the motor current by control calculation, forms a PWM signal according to the duty command value for each phase, and an inverter based on the PWM signal The present invention relates to a motor control device for driving a motor, and the object of the present invention is to provide a one-shunt type having an A / D converter connected to a power source side or a ground side of the inverter to detect each phase current of the motor A current detection circuit, a PWM output position changing unit for outputting the PWM signal by fixing a PWM signal corresponding to the duty command value of each phase at a predetermined position of a carrier cycle, and a duty shift for shifting the PWM signal in a predetermined direction and parts, and the current detection timing determining unit for fixing the current detection timing of a / D conversion by detecting the phase currents of the motor to three points so as to correspond to the predetermined position, the conductive The detected current value detected at the detection timing and a current detection processing unit for processing in accordance with the shifted PWM signals, is achieved by detect the phase currents on the output of the current detection unit, The motor is a three-phase motor, and the predetermined position is the forefront, center and end of the carrier cycle, and the predetermined direction is the front to back, the center back and forth, and the end to front, or The current detection timing is fixed to a position offset by a predetermined time from the front of the carrier period to the rear, a center of the carrier period, and a position offset by a predetermined time from the end of the carrier period to the front. Or the current detection processing unit sequentially supplies the current between the current detection timing and the duty command value for each phase. By performing the current detection processing on the basis of the detectable pattern is more effectively achieved.

  By mounting the motor control devices, the above-described electric power steering device can be achieved.

  According to the present invention, the arrangement of the duty command values for each phase is fixed with respect to the carrier period, and the A / D conversion is performed at a fixed timing position, so that all the detailed calculations are eliminated. The processing capacity of the CPU can be reduced, and the cost can be reduced. That is, in the present invention, the current detection point is fixed at a predetermined offset time from the forefront and end of the carrier cycle and the center of the carrier cycle for each phase on the premise of the timing position of A / D conversion, and the fixed current detection point. The duty command values are arranged at the three locations at the forefront, center, and last of the carrier cycle with reference to, so that the frequency of the duty command values of the phases that are not current detection targets is basically reduced. In addition, the area in which A / D conversion is effective can be increased, and the arithmetic processing capability of the CPU can be reduced. For example, if the current control cycle is 250 μs and the PWM carrier cycle is 50 μs, it is sufficient to output the duty command value to the determined phase once in 250 μs as it is. There is no need to prepare for current detection.

  In addition, since A / D conversion is performed at a current detection timing fixed at three points, there is an effect that the current detection accuracy can be improved and the validity of the current detection value can be confirmed. Further, although noise is generated depending on the current, since it can be patterned, there is an advantage that it is easy to cope with noise reduction.

It is a lineblock diagram showing an outline of an electric power steering device. It is a block diagram which shows the general structural example of a control unit. It is a connection diagram which shows the structural example of a PWM control part and an inverter. It is a connection diagram which shows the structural example of a 1 shunt-type current detection circuit. It is a current path figure which shows the example of a current detection operation | movement of the inverter provided with the 1 shunt-type current detection circuit. It is a current path figure which shows the example of a current detection operation | movement of the inverter provided with the 1 shunt-type current detection circuit. It is a characteristic view for demonstrating the principle of this invention. It is a characteristic view which shows an example of arrangement | positioning of a duty command value, and an electric current detection timing. It is a block diagram which shows the structural example of this invention. It is a flowchart which shows the operation example of this invention. It is a characteristic view which shows the other example of each phase Duty command value and current detection timing. It is a characteristic view which shows the other example of each phase Duty command value and current detection timing. It is a characteristic view which shows the other example of each phase Duty command value and current detection timing. It is a characteristic view which shows the other example of each phase Duty command value and current detection timing. It is a characteristic view which shows the other example of each phase Duty command value and current detection timing. It is a figure for demonstrating the time difference absorption of an electric current detection timing.

The present invention calculates, for example, each phase (U phase, V phase, W phase) Duty command value for controlling the current of a three-phase brushless DC motor, and outputs a PWM signal according to the calculated each phase Duty command value. Each phase PWM signal is fixed at a predetermined position (frontmost, middle, last) of the carrier period, and shifted in a predetermined direction (frontmost, forward, middle, front-back, last-back), one phase or two phases simultaneously By generating the current detection timing at which the PWM signal is turned on at a fixed position of the carrier cycle, the current detection can be performed reliably, and the motor control device is designed to be compact, lightweight, and cost-saving. This is an electric power steering device in which an assist force by a motor is applied to a steering system of a vehicle using a motor control device .
In the motor control device of the present invention, a single current detection circuit (one shunt type current detection circuit) is provided between the inverter and the power supply or between the inverter and the ground (GND), and the detected current value is digitized. An A / D converter for processing is provided. The current detection timing by the single shunt type current detection circuit is fixed at three locations with respect to the carrier cycle of the carrier signal (predetermined time offset from the front, predetermined time offset from the center, and backward from the end), and the current The detection timing is determined in consideration of the A / D conversion timing of the A / D conversion unit and the inverter dead time.

FIG. 7 shows the principle of the present invention, and FIG. 7 (A) shows a carrier signal composed of a sawtooth wave having a carrier period TC (for example, 50 μs), and FIGS. 7 (B), (C), (D ) Respectively indicate U-phase, V-phase, and W-phase duty command value outputs. For the U phase, for example, as shown in FIG. 7B, the U phase Duty command value Du is set to shift forward from the forefront (start position) of the carrier cycle TC, and for the V phase, for example, As shown in FIG. 7C, the V-phase duty command value Dv is set so as to shift evenly forward and backward from the center of the carrier cycle TC. For the W phase, for example, as shown in FIG. The W-phase duty command value Dw is set so as to shift backward from the end (end point position) of the carrier cycle TC. The phase shift of the U-phase Duty command value Du is performed by expanding it in accordance with the Duty width from the forefront of the carrier cycle TC, and the phase shift of the V-phase Duty command value is performed at the center (1/2 position) of the carrier cycle TC. From the end of the carrier cycle TC, the phase shift of the W-phase Duty command value is performed backward in accordance with the Duty width. In this setting, within the same carrier cycle TC, the U-phase Duty command value Du is output before the V-phase Duty command value Dv and the W-phase Duty command value Dw, and the V-phase Duty command value Dv is The W-phase duty command value Dw is output after the duty command value and before the W-phase duty command value Dw. The W-phase duty command value Dw is output after the U-phase duty command value Du and the V-phase duty command value Dv. Once set by the system, the positional relationship of the duty command value does not change until the end. The sum relation of the duty command values in the carrier cycle TC is expressed by the following formula 1.
(Equation 1)
Du + Dv + Dw = 150%
Further, Cu indicates a current detection point (A / D conversion point) mainly using the U phase, and Cv indicates a current detection point (A / D conversion point) mainly using the V phase. Cw indicates a current detection point (A / D conversion point) mainly for the W phase. A current detection point is set at a position where the PWM signal is turned ON simultaneously for one phase or two phases, and the U-phase current detection point Cu is an offset from the forefront of the carrier cycle TC to the A / D conversion timing. The W-phase current detection point Cw is an offset from the end of the carrier cycle TC to the A / D conversion timing. The V-phase current detection timing Cv is set at the center of the carrier cycle TC.

  Note that the forefront, center, and last assignment of the carrier period are arbitrary for the U to W phases, and for example, the V phase may be the forefront of the carrier period.

  Further, as shown in FIG. 7B, in order to detect the U-phase motor current Iu, current detection and A / D conversion are performed at a fixed current detection timing Cu shifted backward by the offset time Tu from the forefront of the carrier cycle TC. However, the offset time Tu is fixed to 0 to 4 times (about 0 to 8 μs) of the dead time of the PWM signal (usually about 2 μs) in consideration of the delay of current and the A / D conversion time. As shown in FIG. 7C, in order to detect the V-phase motor current Iv, current detection and A / D conversion are performed at a current detection timing Cv fixed at the center of the carrier cycle TC. As shown in FIG. 7D, in order to detect the W-phase motor current Iw, current detection and A / D conversion are performed at a fixed current detection timing Cw shifted forward by the offset time Tw from the end of the carrier cycle TC. However, the offset time Tw is fixed to 0 to 4 times (about 0 to 8 μs) of the dead time of the PWM signal (usually about 2 μs) in consideration of the delay of current and the A / D conversion time.

  FIG. 8 shows an example of the timing of motor current detection when the duty command values for each phase are of equal width and the duty command values do not overlap at the phase current detection positions Cu, Cv, Cw. That is, the U-phase motor current Iu is A / D converted at the current detection timing Cu phase-shifted forward by the offset time Tu from the forefront of the carrier cycle TC, and the V-phase current Iv is detected at the center of the carrier cycle TC. A / D conversion is performed at the current detection timing Cv, and the current is detected. The W-phase current Iw is A / D converted at the current detection timing Cw that is phase-shifted backward by the offset time Tw from the end of the carrier cycle TC. To do. Note that, for example, a U-phase and W-phase two-phase motor current may be detected, and the V-phase current Iv may be obtained by Iv = − (Iu + Iw).

  Next, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 9 is a block diagram showing an example of the overall configuration of the motor control apparatus according to the present invention, and includes a CPU 110 that controls the entire motor control apparatus and performs arithmetic processing. The CPU 110 receives a voltage control value E and calculates a duty command value for each phase, a carrier signal input unit 114 for inputting a carrier signal (carrier cycle TC), and a PWM signal for each phase duty command. PWM output position changing unit 111 for fixing the value at a predetermined position of carrier cycle TC, Duty shift unit 112 for shifting each fixed phase duty command value in a predetermined direction, current detection point Cu and each phase duty command value A current detection processing unit 113-1 that performs current detection processing # 1 based on the relationship; a current detection processing unit 113-2 that performs current detection processing # 2 based on the relationship between the current detection point Cv and each phase duty command value; , Current detection processing unit 113-3 that performs current detection processing # 3 based on the relationship between current detection point Cw and each phase duty command value, and current of any phase in current detection processing # 1 to # 3 A current detection section 113-4 that performs current detection processing # 4 in the case where not detected is connected.

  The CPU 110 further outputs a current detection required duty amount setting unit 115 that sets the current detection required duty amount (τ%) as a parameter, and outputs each phase PWM signal based on the calculated each phase duty command value to drive the gate. A PWM signal output unit 116 applied to the unit 105B, a current input unit 117 for inputting a digital value motor current Im (Iu, Iv, Iw) detected by the one-shunt current detection circuit 120 and A / D converted; A current detection timing determination unit 118 that determines a current detection timing (Cu, Cv, Cw) with a predetermined time offset from the forefront of the carrier period and a predetermined time offset from the center and the end of the carrier period is connected.

  FIG. 10 shows an example of the operation of the present invention. A duty amount required for current detection is set by the current detection required duty amount setting unit 115 (step S1), and the duty calculation is performed in consideration of the set required duty amount. The unit 105A calculates a U-phase duty command value, a V-phase duty command value, and a W-phase duty command value based on the voltage control value E (step S2), and generates each phase PWM signal (step S3). Then, the current detection timing determination unit 118 determines the offset times Tu and Tw based on the above-described offset and sets the current detection points Cu and Cw. For the V phase, the center of the carrier cycle TC is set as the current detection timing Cv. Set (step S4). Thereby, the current detection point of each phase is fixed.

Next, the relationship between the current detection point Cu and each phase duty command value, that is, whether or not each phase duty command value Du, Dv, Dw exists on the A / D conversion point Cu is determined. Then, the current detection processing unit 113-1 performs current detection processing # 1 (step S10).

表１の電流検出処理＃１では、（Ｄｕ−Ｔｕ）＞０のとき、電流検出ポイントＣｕ上にＵ相Duty指令値Ｄｕが存在すると判定し、（Ｄｖ−（ＴＣ−２Ｔｕ））＞０のとき、電流検出ポイントＣｕ上にＶ相Duty指令値Ｄｖが存在すると判定し、（Ｄｗ−（ＴＣ−Ｔｕ））＞０のとき、電流検出ポイントＣｕ上にＷ相Duty指令値Ｄｗが存在すると判定する。

In the current detection process # 1 in Table 1, when (Du−Tu)> 0, it is determined that the U-phase Duty command value Du exists on the current detection point Cu, and (Dv− (TC−2Tu))> 0. When it is determined that the V-phase duty command value Dv exists on the current detection point Cu, and when (Dw− (TC−Tu))> 0, it is determined that the W-phase duty command value Dw exists on the current detection point Cu. To do.

Next, the relationship between the current detection point Cv and each phase duty command value, that is, whether or not each phase duty command value Du, Dv, Dw exists on the A / D conversion point Cv is determined. Then, the current detection processing unit 113-2 performs current detection processing # 2 (step S20).

表２の電流検出処理＃２では、（Ｄｕ−ＴＣ／２）＞０のとき、電流検出ポイントＣｖ上にＵ相Duty指令値Ｄｕが存在すると判定し、Ｄｖ＞０のとき、電流検出ポイントＣｖ上にＶ相Duty指令値Ｄｖが存在すると判定し、（Ｄｗ−ＴＣ／２）＞０のとき、電流検出ポイントＣｖ上にＷ相Duty指令値Ｄｗが存在すると判定する。

In the current detection process # 2 in Table 2, when (Du−TC / 2)> 0, it is determined that the U-phase duty command value Du exists on the current detection point Cv. When Dv> 0, the current detection point Cv is determined. It is determined that the V-phase duty command value Dv exists above, and when (Dw−TC / 2)> 0, it is determined that the W-phase duty command value Dw exists on the current detection point Cv.

Next, the relationship between the current detection point Cw and each phase Duty command value, that is, whether or not each phase Duty command value Du, Dv, Dw exists on the A / D conversion point Cw is determined. Then, the current detection processing unit 113-3 performs a current detection process # 3 (step S30).

表３の電流検出処理＃３では、（Ｄｕ−（ＴＣ−Ｔｗ））＞０のとき、電流検出ポイントＣｗ上にＵ相Duty指令値Ｄｕが存在すると判定し、（Ｄｖ−（ＴＣ−２Ｔｗ））＞０のとき、電流検出ポイントＣｗ上にＶ相Duty指令値Ｄｖが存在すると判定し、（Ｄｗ−Ｔｗ）＞０のとき、電流検出ポイントＣｗ上にＷ相Duty指令値Ｄｗが存在すると判定する。

In the current detection process # 3 in Table 3, when (Du− (TC−Tw))> 0, it is determined that the U-phase Duty command value Du exists on the current detection point Cw, and (Dv− (TC−2Tw) )> 0, it is determined that the V-phase duty command value Dv exists on the current detection point Cw, and when (Dw−Tw)> 0, it is determined that the W-phase duty command value Dw exists on the current detection point Cw. To do.

After the current detection processes # 1 to # 3, it is determined whether or not the currents Iu, Iv, and Iw of all phases have been detected (step S40), and the current of any phase has not been detected. The current detection processing unit 113-4 obtains an undetected phase current according to the following Table 4.

図１１は電流検出の他のサンプリング例を示しており、Ｕ相Duty指令値が拡大し、電流検出ポイントＣｖでＵ相及びＶ相のDuty指令値が重なった場合である。この場合には、Ｕ相電流Ｉｕは電流検出タイミングＣｕで電流検出及びＡ／Ｄ変換して求め、Ｖ相電流Ｉｖは“電流検出タイミングＣｖの電流値Ｉｖ−電流検出タイミングＣｕの電流値Ｉｕ”又はＩｖ＝−（Ｉｕ＋Ｉｗ）で求め、Ｗ相電流Ｉｗは電流検出タイミングＣｗで電流検出及びＡ／Ｄ変換して求める。

FIG. 11 shows another sampling example of current detection, in which the U-phase duty command value expands and the U-phase and V-phase duty command values overlap at the current detection point Cv. In this case, the U-phase current Iu is obtained by current detection and A / D conversion at the current detection timing Cu, and the V-phase current Iv is “current value Iv at the current detection timing Cv−current value Iu at the current detection timing Cu”. Alternatively, Iv = − (Iu + Iw) is obtained, and the W-phase current Iw is obtained by current detection and A / D conversion at the current detection timing Cw.

Figure 12 shows another sampling example of the current detection is when the U-phase Duty command value is further expanded, Duty command value at the detection position C v and C w are overlapped. In this case, the U-phase current is detected and A / D converted at the current detection timing Cu, and the V-phase current is “current value Iv at current detection timing Cv−current value Iu at current detection timing Cu” or Iv = −. The I-phase current is obtained by (Iu + Iw), and the W-phase current is obtained by current detection and A / D conversion at “current value Iw at current detection timing Cw−current value Iu at current detection timing Cu”.

FIG. 13 shows still another sampling example of current detection, in which the V-phase duty command value expands and the V- phase and W-phase duty command values overlap at the current detection point Cw. In this case, the U-phase current Iu is obtained by current detection and A / D conversion at “current value Iu of current detection timing Cu−current value Iv of current detection timing Cv”, and the V-phase current Iv is determined by the current detection timing Cv. in seeking, W-phase current Iw determined by the current detection and a / D conversion in the "current value of the current detection timing Cw Iw- current detection timing C v of the current value I v".

  FIG. 14 shows still another sampling example of current detection, when the duty command values of the U phase, V phase, and W phase are all expanded, and the duty command values overlap at the current detection points Cu, Cv, and Cw. It is. In this case, the U-phase current Iu is obtained by Iu = − (Iv + Iw), the V-phase current Iv is obtained by Iv = − (Iu + Iw), and the W-phase current Iw is obtained by Iw = − (Iu + Iv).

FIG. 15 shows still another sampling example of current detection, in which the U-phase duty command value is reduced and the duty command value is not satisfied at the current detection point Cu. In this case, the U-phase current Iu is obtained by Iu = − (Iv + Iw), and the V-phase current Iv is “current value Iv at current detection timing Cv−current value Iw at current detection timing Cw”. The W-phase current Iw is obtained by current detection and A / D conversion at the current detection timing Cw .

FIG. 16 is a diagram for explaining time difference absorption of current detection timing. In the above description, for the sake of simplicity, the description has been made in the same carrier period (section DA in FIG. 16 ). However, it is desirable that the time difference in current detection for each phase is as small as possible. Therefore, it is possible to reduce the time difference of current detection by using the Duty output of the adjacent carrier period and its A / D conversion value (section DB in FIG. 16). In order to increase the accuracy of current detection, it is better to synchronize A / D conversion. In FIG. 16, the current detection point Cu and the current detection point Cw appear to be separated from each other. The current detection point Cu and the current detection point Cw can be suppressed within the range of the section DB. However, in order to perform this current detection strictly, it is premised that the same PWM-Duty command value is also output in at least one adjacent carrier cycle.

  In the above description, the three-phase brushless motor has been described, but the same control is possible for the motors of other phases.

1 Steering Handle 10 Torque Sensor 12 Vehicle Speed Sensor 13 Battery 20 Motor 21 Resolver 22 Angular Speed Calculation Unit 100 Control Unit 101 Steering Auxiliary Command Value Calculation Unit 102 Maximum Output Limiting Unit 104 Current Control Unit 105 PWM Control Unit 105A Duty Calculation Unit 105B Gate Drive Unit 106 Inverter 110 CPU
111 PWM output position changing unit 112 Duty shift unit 113-1 Current detection processing unit # 1
113-2 Current detection processing unit # 2
113-3 Current detection processing unit # 3
113-4 Current detection processing unit # 4
114 Carrier signal input unit 115 Current detection required duty amount setting unit 116 PWM signal output unit 117 Current input unit 118 Current detection timing determination unit 120 One shunt type current detection circuit

Claims (8)

Motor control for calculating each phase duty command value for controlling the motor current by control calculation, forming a PWM signal corresponding to each phase duty command value, and driving the motor by an inverter based on the PWM signal In the apparatus, a one-shunt current detection circuit having an A / D conversion unit is connected to a power supply side or a ground side of the inverter,
The PWM signal corresponding to each phase Duty command value is fixed at a predetermined position of a carrier cycle, and the PWM signal is shifted in a predetermined direction.
A motor control device characterized in that a current detection timing for detecting A / D conversion by detecting each phase current of the motor is fixed at three points corresponding to the predetermined position. The current detection timing is fixed to a position offset by a predetermined time from the front of the carrier period to the rear, a center of the carrier period, and a position offset by a predetermined time from the end of the carrier period to the front. The motor control device according to claim 1. The motor control device according to claim 2, wherein the predetermined time is 0 to 4 times the dead time of the inverter. Motor control for calculating each phase duty command value for controlling the motor current by control calculation, forming a PWM signal corresponding to each phase duty command value, and driving the motor by an inverter based on the PWM signal In the apparatus, a one-shunt current detection circuit having an A / D converter connected to the power source side or the ground side of the inverter to detect each phase current of the motor, and according to the duty command value of each phase A PWM output position changing unit that outputs the PWM signal by fixing the PWM signal at a predetermined position of a carrier cycle, a duty shift unit that shifts the PWM signal in a predetermined direction, and detects each phase current of the motor A current detection timing determination unit for fixing current detection timing for A / D conversion at three points corresponding to the predetermined position; and current detection detected at the current detection timing A current detection processing unit for processing a value according to the shifted PWM signal ,
Motor control device characterized in that it detect the phase currents on the output of the current detection unit. 5. The motor according to claim 4, wherein the motor is a three-phase motor, and the predetermined position is the forefront, center, and end of the carrier cycle, and the predetermined direction is the back from the front, the front / rear from the center, and the front from the end. The motor control apparatus described. The current detection timing is fixed to a position offset by a predetermined time from the front of the carrier period to the rear, a center of the carrier period, and a position offset by a predetermined time from the end of the carrier period to the front. The motor control device according to claim 5. The motor control device according to claim 5 or 6, wherein the current detection processing unit performs current detection processing on the basis of a current detectable pattern of the current detection timing and the duty command value sequentially for each phase. An electric power steering apparatus comprising the motor control device according to any one of claims 1 to 7.

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